Nevertheless, aside from ruffling feathers by making his call at the beginning of Ramadan, there are several question marks over David Cameron’s comments. Most broadly, it has to be wondered whether such a very public call to action is likely to strike a chord. The issues under discussion are, after all, nuanced and sensitive. A set-piece speech at a security conference in Slovakia feels like the response of a remote headmaster during all-school assembly, when the message might have been delivered better face-to-face by individual form tutors.

For all the talk about the need for better integration or assimilation, Mr Cameron frequently gives the impression of holding to a lofty “them and us” dichotomy, which is hardly an ideal way to encourage a sense of belonging among young British Muslims.

More especially, the Prime Minister’s description of some Muslims “quietly condoning” Isis is troublingly lacking in clarity. It suggests a sinister but possibly widespread undercurrent of support here for the horrors we see in Iraq and Syria: the beheadings, the rapes of children; the hurling of gay people from tall buildings. Yet we have been presented with no evidence that such bestial acts are supported by any but the most extreme individuals.

No doubt Mr Cameron will say that his remarks were directed at those who, while not justifying these acts, have sympathy with the underlying assumptions about the role of women, say, and the nature of homosexuality. But these are dangerous boundaries to blur.

Furthermore, to speak about “quiet condoners” casts suspicion on any Muslim who simply wishes to get on with their own life and has no desire to speak out about anything, let alone religious extremism. Again, Mr Cameron creates an overly simplistic tableau: one in which participants are either loudly disclaiming or silently, secretively excusing.

Nobody doubts that more needs to be done to reduce the numbers of Britons attracted by the fundamentalism and violence of Isis and its followers. But their motivation appears to be extraordinarily complex and every exhortation requiring this group or that agency to be more vigilant, or less acquiescent, masks the intricate nature of the problem.

Likewise, such declarations tend to overstate the impact of whichever community or organisation is the target of the day. Britain’s Muslims are hardly ignorant of how Isis seeks new recruits. Those who have been lost to extremism are not faceless clones. They are sons, daughters, siblings, fathers and mothers, whose flight to the Middle East causes immense pain to those they leave behind. To think Muslim communities deliberately ignore a magic switch that would stop more desperation and death is to overestimate the power of the collective over individual will.

The Government has a difficult task on its hands and the Prime Minister recognises, rightly, that the security services, communities, schools and families all have their parts to play in tackling Isis’s pull. But Mr Cameron must beware ill-judged phrases if he is to keep all the relevant actors on side.